It seems like just weeks ago that Castle aired its season 4 premiere, with eager fans waiting to see the fall out of Castle’s vocal expression of love. But in typical Castle/Beckett fashion, things didn’t play out exactly how we expected.

Season four found the pair largely avoiding the issue – and, in Beckett’s case, dealing with emotional problems along the way. But it was clear to everyone around them that they were as crazy as ever about one another. Tonight, they finally make it clear to each other, as EW showed you on Friday in this exclusive clip. “The episode is really about what secrets come out,” says executive producer Andrew Marlowe.

And those secrets are multi-layered. Not only will Castle and Beckett finally hash it out over their feelings (“She doesn’t know that he knows that she heard the ‘I love you.’ That comes out,” he says), but when a case finds Beckett once again working her mother’s murder case, Castle might have to come clean about another secret he’s been keeping.

“When this case rears it’s head, her safety tends to be at risk and Castle gets concerned. This puts him in immediate conflict with what he’s suppose to be doing in terms of protecting her – you know, the mysterious phone call he got at the beginning of the season and what that entails,” says Marlowe. “And Castle has basically been keeping this secret from her all season. And at some point, when she’s driving flat out for the wall, and he’s got to get her off the pathway, those secrets come out. It fundamentally alters their relationship.”

The question is will it be for better or worse? As per usual when Beckett is working her mother’s case, Marlowe says both characters are “in a difficult situation” during the hour, and it will, ultimately, cause emotional fractures in them both. “Early on in the episode, when Beckett is wondering what this has to do with anything, she says, ‘These guys tried to kill me and then nothing for a year, and every morning I wake up wondering if they other shoe is going to drop. What if this is the other shoe?’ That’s her mental state in the episode,” he says.

Make sure you come back to InsideTV tonight after the west coast airing (2 a.m. ET) for some of Marlowe’s thoughts on the season finale!